1. Field of the Invention
The present invention relates to a polishing pad and a manufacturing method thereof, and more particularly, to an integral polishing pad in which an elastic support layer and a polishing layer are integrated, and a manufacturing method thereof.
2. Description of the Related Art
Polishing speed and planarization performance are important in chemical mechanical polishing which is introduced for global planarization with the development of highly integrated and microscopic semiconductor devices and multilayer wiring structures. These are determined depending on the conditions of polishing equipment, the type of polishing slurry, the type of polishing pad, and the like. In particular, a polishing pad, which is in direct contact with a wafer during polishing and is an expendable element, is an important factor determining the polishing performance.
In U.S. Pat. No. 5,257,478, an improved polishing pad, which minimizes a hysteresis loss by elastically compressing and expanding with respect to down pressure induced by a wafer during a polishing operation so that planarization efficiency is improved, is disclosed. The polishing pad includes a resilient base layer, which is volume compressible, and a top planarizing layer, which is less volume compressible than the resilient base layer. These two layers are connected to each other by an incompressible adhesive. However, the resilient base layer cannot effectively act when the adhesive is nonuniformly applied, and therefore, the planarization efficiency is decreased. In addition, applying the adhesive for connection of the two layers when manufacturing the polishing pad complicates manufacturing processes.
In the meantime, it is important to accurately and quickly detect the flatness of a wafer during a polishing operation. Accordingly, polishing pads suitable for optically detecting the flatness of a wafer in situ are disclosed in U.S. Pat. Nos. 5,605,760 and 6,171,181. However, for the polishing pad disclosed in U.S. Pat. No. 5,605,760, it is necessary to punch a pad and attach a window transparent to a light beam, so manufacturing processes are complex. In addition, a gap at a connection between the transparent window and the pad hinders the delivery of a polishing slurry, and a lump of the polishing slurry collected at the gap may scratch the surface of a wafer. Since the material of the transparent window is different from that of the pad, a crack may occur around the transparent window during a polishing operation. In U.S. Pat. No. 6,171,181, the polishing pad including a transparent region formed by more quickly solidifying a predetermined region than any other region in a mold is disclosed. However, in order to manufacture this polishing pad, a special mold in which temperature can be differently adjusted depending on portions is required, and therefore, manufacturing cost is increased. Moreover, since hysteresis loss cannot be minimized only by using a pad disclosed in U.S. Pat. No. 5,605,760 or 6,171,181, an elastic support layer is also required. Here, it is necessary to form a transparent window or a transparent region in the elastic support layer, so manufacturing processes become complex.